1. Field of the Invention
The present invention relates to a transmitter, a receiver, a communication apparatus, and a communication method capable of executing a centralization process of digital data by concentrating the digital data, which being transmitted from a plurality of external devices which enable execution of data exchange at their natural transmission speeds respectively or being transmitted from an external network, to a common data transfer line, a common multiplexer, or a common distributor, and also capable of implementing smooth two-way communications between the external network and the plurality of external devices or between the plurality of external devices.
The present invention also relates to a communication system constructed by connecting a plurality of communication apparatuses via a data transmission line to execute data exchange between the plurality of communication apparatuses and, more particularly, a communication system capable of implementing smooth two-way communications between the plurality of communication apparatuses.
The present invention also relates to a communication system constructed by connecting a plurality of communication apparatuses, to which one external device or more than two external devices being connected respectively, via a data transmission line to execute data exchange between any external devices, between any communication apparatuses, or between any external device and any communication apparatus and, more particularly, a communication method and a communication system capable of improving a communication efficiency remarkably by avoiding surely collision between communication data.
2. Description of the Prior Art
As protocols for communication devices or apparatuses commonly used in the prior art, D2B (Audio, video and audiovisual systems Domestic Digital Bus: CIE/IEC 1030) employed to transmit digital audio data, etc.; standard which conforms to a recommendation made by CCITT (International Telegraph and Telephone Consulting Committee) and is used to execute personal computer communication, etc.; USB (Universal Serial Bus) and IEEE1394 used to connect personal computer peripheral devices such as a keyboard, a CRT display, a mouse, a modem, and a printer to a personal computer main body; ATAPI (AT Attachment Packet Interface) used as an interface to connect devices such as a DVD (Digital Video Disc or Digital Versatile Disc)-ROM drive, or a music CD (Compact Disc) player; MPEG2 (Moving Picture Image Coding Experts Group Phase2: ISO/IEC13818) which is a full color moving picture compression scheme for a digital TV set, etc.; ATM (Asynchronous Transfer Mode) for a computer and a digital TV set; and the like, for example, have been known.
In recent, there has been caused a request to implement a centralization process by concentrating sound data or video data supplied from various vehicle-equipped devices such as a radio, a mobile telephone, a TV set, a CD player, a navigation system; speed data supplied from a speed sensor; moving orientation data supplied from a geomagnetism sensor; data of running conditions of the vehicle such as the distance data between own vehicle and the next vehicle ahead running in the same direction, and the like. The reason for such centralization process is that, if such centralization process can be executed by concentrating output data supplied from various vehicle-equipped devices, various sensors, and forth arranged in various locations of the vehicle, mutual output data can be commonly used by respective vehicle-equipped devices, and simultaneously necessary data can be communicated at once when an vehicle-vehicle communication to execute data communication between own vehicle and another vehicle and a road-vehicle communication to execute data communication between own vehicle and stations arranged along the running route should be conducted, so that convenience of the vehicle can be improved.
With the above mentioned protocols, communication speeds, data formats, etc. have been specified individually according to respective protocols without regard to compatibility or interchangeability of communications in the existing circumstances. Accordingly, in the event that data communication should be executed between the vehicle-equipped devices which have mutually different protocols respectively, for example, in general personal computers in which an interface and a communication control unit both being constructed to enable communications between object protocols are built in previously have been connected to respective vehicle-equipped devices and then personal computer communications through such personal computers have been carried out.
However, in such data communications between the vehicle-equipped devices, there have been many limitations to construct a system, e.g., the personal computers have to be connected to respective vehicle-equipped devices. Such many limitations have made it difficult to improve flexibility of the system and have become obstacles to construction of the communication system such as the vehicle-vehicle communication or the road-vehicle communication for which the centralization process of data is requested.